title: Antimicrobial activity among multidrug-resistant Streptococcus pneumoniae isolated in the United States, 2001-2005.
abstract: Infections caused by multidrug-resistant (MDR) Streptococcus pneumoniae remain a major concern when selecting an appropriate antimicrobial agent. In this analysis, 27 781 isolates of S pneumoniae collected from 2001 to 2005 in the United States were tested for MDR phenotypes. About 25% of all isolates were MDR, defined as resistant to 2 or more of the following agents: cefuroxime, a macrolide, penicillin, tetracycline (if available), and trimethoprim-sulfamethoxazole (TMP-SMX). There was a slight decreasing trend over time in multidrug resistance prevalence with erythromycin. Among MDR strains, the most common coresistance pair was erythromycin and TMP-SMX (74% of isolates, irrespective of resistance to other agents), although penicillin-erythromycin and penicillin-TMP-SMX coresistance patterns were also found in more than 56% of MDR strains. Resistance to 4 antimicrobial agents tested was observed in 33% of all antimicrobial-resistant isolates. Levofloxacin, which was used as a representative of the fluoroquinolone class, was active against at least 98% of all MDR isolates, and the minimum inhibitory concentration (90%) (MIC(90)) for this population was 1 microg/mL (identical to the total S pneumoniae, population). Multidrug-resistant isolates from 2003 to 2005 were found to be equally susceptible (98%) to other respiratory fluoroquinolones (gatifloxacin and moxifloxacin; data not shown), although only 88% of MDR isolates (from 2001-2005) were susceptible to ciprofloxacin. Careful monitoring of multidrug resistance patterns will help guide appropriate therapeutic selection and may provide early detection of changes in resistance to more potent agents.
authors.affiliation: Eurofins Medinet, Inc., Herndon, VA 20171, USA.
authors.forename: Clyde
authors.initials: C
authors.lastname: Thornsberry
authors.forename: Nina P
authors.initials: NP
authors.lastname: Brown
authors.forename: Deborah C
authors.initials: DC
authors.lastname: Draghi
authors.forename: Alan T
authors.initials: AT
authors.lastname: Evangelista
authors.forename: Y Cheung
authors.initials: YC
authors.lastname: Yee
authors.forename: Daniel F
authors.initials: DF
authors.lastname: Sahm
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D024901:Drug Resistance, Multiple, Bacterial; D006801:Humans; D008826:Microbial Sensitivity Tests; D011008:Pneumococcal Infections / Q000453:epidemiology / Q000382:microbiology*; D011159:Population Surveillance; D012141:Respiratory Tract Infections / Q000453:epidemiology / Q000382:microbiology*; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000302:isolation & purification; D014481:United States / Q000453:epidemiology
chemical_list: D000900:Anti-Bacterial Agents